add support for epics and project tags

[rafleze]

I hope this updates will be useful.
These changes are needed.
Thank you for this great job.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@012d7ca). Click here to learn what that means.
The diff coverage is 55.17%.

@@            Coverage Diff            @@
##             master      #77   +/-   ##
=========================================
  Coverage          ?   96.22%           
=========================================
  Files             ?        7           
  Lines             ?      848           
  Branches          ?       67           
=========================================
  Hits              ?      816           
  Misses            ?       20           
  Partials          ?       12

Impacted Files	Coverage Δ
taiga/models/__init__.py	100% <ø> (ø)
taiga/client.py	92.15% <100%> (ø)
taiga/models/models.py	96.38% <53.57%> (ø)

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[marchaase]

any progress on getting this merged in?

[fmarco]

@rafleze Thank your for this PR, we'll have a look as soon as possibile!

[yakky]

@rafleze @morlandi is there a way we can merge #77 and #66 they both needs the improvements of the other
Let's talk about the way to cooperate to get both merged

[yakky]

merged with #66